text: Evapoporometry uses modified forms of the Kelvin equation to relate the evaporation of a wetting liquid (usually 2-propanol) from a membrane to the average diameter of the pores in that membrane. The primary equation used in this technique is:
  Where  is the pore diameter,  is the surface tension,  is the vapor molar volume,  is the gas constant,  is the absolute temperature,  is the instantaneous evaporation rate in , and  is the average evaporation rate of the free-standing liquid layer in .